diff --git a/src/middlewared/middlewared/plugins/pool.py b/src/middlewared/middlewared/plugins/pool.py
index f77f5d2f7ed37..20b05babab5f5 100644
--- a/src/middlewared/middlewared/plugins/pool.py
+++ b/src/middlewared/middlewared/plugins/pool.py
@@ -54,7 +54,13 @@ def validate(self, value):
 
     def to_json_schema(self, parent=None):
         schema = self.value.to_json_schema(parent)
-        schema['anyOf'] = [{'type': schema.pop('type')}, {'type': 'string', 'enum': ['INHERIT']}]
+        type_schema = schema.pop('type')
+        schema['nullable'] = 'null' in type_schema
+        if schema['nullable']:
+            type_schema.remove('null')
+            if len(type_schema) == 1:
+                type_schema = type_schema[0]
+        schema['anyOf'] = [{'type': type_schema}, {'type': 'string', 'enum': ['INHERIT']}]
         return schema
 
 
diff --git a/src/middlewared/middlewared/schema.py b/src/middlewared/middlewared/schema.py
index a08709791b5b3..28dc75d2dbc35 100644
--- a/src/middlewared/middlewared/schema.py
+++ b/src/middlewared/middlewared/schema.py
@@ -142,6 +142,7 @@ def to_json_schema(self, parent=None):
                 {'type': 'array'},
             ],
             'title': self.title,
+            'nullable': True if self.null else False
         }
         if self.description:
             schema['description'] = self.description